3,445,506 United States Patent Office Patented May 20, 1969 2 utilized more efficiently by using excess in 3,445,506 the various steps. Excess sulfuric acid increases unde METHOD FOR PREPARING ETHYL ACRYLATE Stephen Soga, Avon Lake, Ohio, assignor to The B. F. sired ammonium bisulfate as a by-product of the Goodrich Company, New York, N.Y., a corporation of esterification reaction and unless the unreacted Sulfuric New York acid can be recycled as it is in accordance with this in No Drawing. Filled Jan. 21, 1966, Ser. No. 522,021 vention, the costs of the process become excessive. In Int, C. C07c67/00, 103/08 this process only about one pound of sulfuric acid and U.S. C. 260-486 6 Claims oleum per pound of ethyl acrylate obtained is used as compared to a predicted use of about two pounds of O Sulfuric acid per pound of ethyl acrylate, as well as only ABSTRACT OF THE DISCLOSURE % as much ammonium sulfate actually formed. The recovered sulfuric acid may be brought to the desired Ethyl acrylate is prepared by reacting acrylamide strength during the recycle operation by heating under sulfate with ethyl sulfates in an integrated process where vacuum to reduce the water content thereof. by by-product , acrylic acid, beta-ethoxy 5 The acrylamide sulfate is readily prepared by reacting ethyl propionate and formed during the reaction, acrylonitrile with, normally, a molar excess of sulfuric along with unreacted sulfuric acid, may be recycled and acid in a concentration of greater than 70% acid. Acids utilized in the process. The acrylamide sulfate and sulfates of concentrations from above 75 to 85% are normally are readily prepared by reaction of acrylonitrile and used. The acrylonitrile is preferably added to a vigorously with sulfuric acid. agitated Sulfuric acid solution in a reactor at an elevated temperature. The reaction is exothermic and usually is controlled at a temperature of about 100° C. This invention relates to production of ethyl acrylate Ethyl sulfates are obtained by reacting sulfuric acid and relates more particularly to the preparation of ethyl and ethylene and/or reacting oleum and sulfuric acid acrylate by means of an improved process based on 25 with recycled diethyl ether and ethylene. In a first step, acrylonitrile, sulfuric acid and ethylene comprising ethylene is charged to the reactor containing fresh 96% esterifying acrylamide sulfate with ethyl sulfate to form Sulfuric acid, at a pressure of about 160 p.s.i.g. or high ethyl acrylate in good yield. er, until the acid content of the charge is reduced to Several methods are known for preparing alkyl esters about 35% sulfuric acid, depending on the concentration of acrylic acid from acrylonitrile. In one such process 30 of ethyl sulfate desired. When recycled diethyl ether is acrylonitrile is reacted with water in the presence of an included in the process, the ethyl sulfate reactor is acid and the reaction product formed further reacted charged with Sulfuric acid and oleum (65%) and the with an to provide the alkyl ester. Another recycled diethyl ether is charged to the reactor to obtain method involves a batch reaction of a nitrile, an olefin the initial ethyl sulfates. The temperature is then adjusted and Sulfuric acid to provide an alkyl ester. The latter 35 to 50 to 70° C. and additional ethylene charged to the process, which is of interest because of the potential use reactor under pressure to obtain the desired ethyl sul of ethylene rather than ethanol, has not been commercial fates for further reaction. ly used because of the long reaction times required and To esterify the acrylamide sulfate, the acrylamide sul low yields of desired product. Processes based on ethyl fate is diluted with water and cooled to about 50 to 70° ene rather than ethanol are desirable for economic rea 40 C. By this technique, the subsequent formation of large SOS amounts of diethyl ether and ethylene on addition of ethyl Accordingly, it is an object of this invention to pro Sulfate is greatly reduced. If the acrylamide sulfate so vide an improved and integrated process for prepar lution is not diluted and cooled the formation of diethyl ing ethyl acrylate on a commercial scale from ethylene ether and ethylene takes place to a degree to make the and acrylonitrile. It is another object of this invention to process uneconomical. The amount of dilution may be provide a commercial process for preparing ethyl acrylate Varied from about four to about eight, preferably five to without formation of excessive amounts of expensive by six mols of water per mol of acrylamide sulfate as a dil products which are difficult to remove and must be dis uent. Put another way, the concentration of arcylamide carded. It is still another object of this invention to pro Sulfate in water and acid preferably should be from about vide an improved and economical process for preparing 40 to about 45%. The ethyl sulfates are then charged ethyl acrylate using acrylonitrile, ethylene and sulfuric 50 to the reactor and the temperature of the reactor raised acid as starting materials to provide a maximum yield to about 90-100° C. During this heating period ethyl of ethyl acrylate with a minimum loss of raw materials acrylate, some water, ethanol and diethyl ether vaporize as unused by-products. and are removed from the reactor and are condensed. These and other objects of the invention are realized The reactor temperature is then increased to about 120° by a process comprising reacting acrylonitrile with sul 55 C. With Superheated recycled ethanol and water from furic acid to form acrylamide sulfate, reacting ethylene previous runs and then raised to about 150° C. to steam with Sulfuric acid to provide ethyl sulfates, then react strip the remainder of the organic reactants and prod ing the acrylamide sulfate with the ethyl sulfates to form lucts present in the reactor. The diethyl ether is separated ethyl acrylate in an integrated process whereby the by. from the ethyl acrylate in a still and recycled to an ethyl product diethyl ether, acrylic acid, beta-ethoxy ethyl 60 Sulfate reactor. The ethanol is extracted with water and propionate and ethanol which are formed during the re recycled as described to sparge the reactor and the ethyl action, and unreacted sulfuric acid, may be recycled and acrylate is distilled to provide polymerization grade ethyl utilized in the process as described more in detail herein acrylate. The high boilers from this distillation are also after. recycled. The residue from the reactor which is am While the reactions may be begun with new or fresh 65 monium bisulfate and sulfuric acid, is centrifuged to sep Sulfuric acid, in the operation of the process recycle sul arate ammonium bisulfate from sulfuric acid. The acid furic acid becomes available and is used in forming is then recycled as described above. acrylamide Sulfate. While theoretically only one mol of 100 to 500 p.p.m. copper sulfate or ferrous sulfate Sulfuric acid is required to obtain one mol of ethyl have been found to be satisfactory inhibitors of polym acrylate from acrylonitrile and ethylene according to 70 erization during the preparation of acrylamide sulfate Stoichiometric equations, the process of this invention is and during reaction of acrylamide sulfate with ethyl 3,445,506 3. 4. Sulfate. The condensed reaction products are stabilized Example II with known polymerization inhibitors during recovery and purification of ethyl acrylate on a basis of about 10 In still another run performed as described in Ex to 1000 p.p.m., usually 25 to 250 p.p.m. of organic stabi ample I, 1.02 mols of sulfuric acid was reacted with 1 lizer such as hydroquinone may be used. mol of acrylonitrile in a ratio of 1.02 mols of sulfuric Specific embodiments of the invention are now de 5 acid, 1.6 mol of water and 1 mol of acrylonitrile and the scribed. resulting product diluted with 5.3 mols of recycle water which contained 0.15 mol of acrylic acid and 0.04 mol of Example I beta-ethoxy ethyl propionate, which are reaction by A sulfuric acid solution is prepared, which may be products and are recovered in the purification of ethyl fresh and/or recycled acid, diluted to 85% concentra O acrylate, and cooled to 70° C. 0.3 mol of diethyl ether tion with a 2% aqueous ferrous sulfate solution. The acid which may be separated in a still in the purification of Was charged to a reactor and maintained at a tempera ethyl acrylate was reacted with a mixture of 1 part oleum ture, in the range of about 96 to 100° C. Acrylonitrile (64%) and 3 parts of 96% sulfuric acid, and thereafter was charged to sulfuric acid solution in the reactor with this mixture was treated with ethylene at 160 p.s.i.g. at vigorous agitation. The acrylonitrile was charged over 5 a temperature in the range of 42° C. to 57 C. until the a 1.1 hour period and was held for an additional hour ethylene had reacted with about 60% of the sulfuric So that a complete reaction in converting the acrylonitrile acid to provide ethyl sulfates. After the esterification re to acrylamide sulfate was obtained. The molar ratio of action and purification as described in Example I, ethyl acrylonitrile to sulfuric acid to water was 1.02 mols of acrylate in a yield of 86% based on acrylonitrile was ob Sulfuric acid and 1.32 mols of water per mol of acryloni 20 tained with less acrylic acid and beta-ethoxy-ethyl pro trile. The ethyl sulfate was prepared by reacting 1.22 pionate being formed than when these latter two mate mols of fresh 96% sulfuric acid at 50 to 70° C. with rials were not recycled, ethylene by passing ethylene into the reactor under a I claim: pressure of at least 160 p.s.i.g. 1.33 mols of ethylene re 25 1. A method for preparing ethyl acrylate from acry acted with sulfuric acid. The acrylamide sulfate solution Ionitrile, ethylene and sulfuric acid which comprises re was diluted with 5.9 mols of water per mol of acrylamide acting acrylonitrile with sulfuric acid to form acrylamide sulfate and cooled to about 60 to 70° C. and the ethyl sulfate, reacting ethylene with sulfuric acid to form ethyl Sulfate charged to the reactor which was then heated to sulfate, mixing said acrylamide sulfate in dilute aqueous about 125° C. in about one half hour. At about 100° C. 30 solution at a temperature below about 85° C. with said product begins to vaporize from the reactor including ethyl sulfates, then heating the resulting mixture to a ethyl acrylate, diethyl ether, water and ethanol. Super temperature above 100° C. and recovering ethyl acry heated vapors of recycle alcohol and water were then late. admitted to the reactor through a sparger and the tem 2. The method of claim 1 wherein the reaction of perature raised from about 126 C, to about 140° C. and acrylonitrile with excess sulfuric acid is controlled at a the ethyl acrylate, alcohol, ether and other materials temperature of about 90-110° C., ethylene is reacted which volatilized were condensed. The reaction mixture with sulfuric acid at a temperature of about 50 to 70° C. was then steam stripped at 148 C. for about one half under a pressure greater than about 100 p.s.i.g., diluting hour. The diethyl ether was separated from the ethyl said acrylamide sulfate with water and cooling to a tem acrylate by distillation, the ethanol by extraction with 40 perature of about 50 to about 70° C. prior to reaction water, and the ethyl acrylate fractionated to provide a with ethyl sulfate, and heating the reaction mixture of product having a purity of about 99%. The acrylic acrylamide sulfate and ethyl sulfate to about 150° C. acid and other high boilers are returned to the esterifica while stripping with steam. tion reactor. The steam stripped residue remaining in 3. The method of claim 2 wherein acrylamide sulfate the reactor after steam distillation contained unreacted is formed by adding acrylonitrile to sulfuric acid having sulfuric acid and aqueous ammonium bisulfate. This was a concentration of about 85%, and diluting the resulting removed from the reactor and allowed to cool so that acrylamide sulfate with 4 to 8 mols of water per mol of the ammonium bisulfate would crystallize. The crystals acrylamide sulfate. were separated by filtration and the sulfuric acid was 4. The method of claim 1 wherein diethyl ether, acrylic recycled for the reaction with acrylonitrile after stripping acid and beta-ethoxy ethyl propionate formed during the water therefrom to increase the concentration of the said reaction of acrylamide sulfate and ethyl sulfate, and sulfuric acid. The yield of ethyl acrylate based on acry unreacted sulfuric acid, are recovered and recycled in lonitrile was 87%. making additional ethyl acrylate by reacting said recycled High boiling acrylic acid and beta-ethoxy ethyl pro sulfuric acid with acrylonitrile, recycling said acrylic pionate which are separated during purification of the acid and beta-ethoxy ethyl propionate to the reactor ethyl acrylate by fractionation are also recycled and in where acrylamide sulfate and ethyl Sulfate are reacted, troduced into the esterification reactor with the recycle and preparing additional ethyl sulfates for recycling to sulfuric acid and this step markedly reduces the net make said reactor by reacting diethyl ether with sulfuric acid of these undesired by-products and improves the utiliza and oleum to form ethyl sulfate. tion of acrylonitrile. 60 5. The method of claim 4, on a continuous basis, wherein said acrylamide sulfate is formed by adding acry Example II lonitrile to about 85% concentrated Sulfuric acid con In another run, following the general procedure of taining 200 to 500 parts per million of copper sulfate Example I set forth above, on a molar basis, one mol of and iron sulfate and water in a molar ratio of one mol acrylonitrile was reacted with 0.98 mol of recycled sul of acrylonitrile, 1 to 2 mols of about 85% fresh or re furic acid which had been concentrated to 85% acid by cycle sulfuric acid, ethylene is reacted with about 96% heating under vacuum and contained 200 p.p.m. ferrous sulfuric acid at a temperature of about 50 to 70° C. under sulfate. The resulting acrylamide sulfate was diluted on pressure in the range of about 160 p.s.i.g., said acrylamide a basis of one mol of acrylamide sulfate with 5.9 mols sulfate is diluted with 4 to 7 mols of water per mol of of water. The ethyl sulfates were prepared as described 70 acrylamide sulfate and cooled to a temperature of about with, on a molar basis, 1.29 mols of sulfuric acid and 50 to 70° C. prior to reaction with ethyl sulfate, the re 1.55 mols of ethylene. A yield of 90% ethyl acrylate action mixture of acrylamide sulfate and ethyl sulfate based on the acrylonitrile was obtained, an unexpected is heated to about 120° C., further heated to about 140° C. increase from use of recycle sulfuric acid which con with superheated recycle ethanol and steam and stripped tained high boiling impurities. 75 at about 145 to 150° C. with steam, wherein the 3,445,506 5 6 volatile reaction products are recovered and diethyl ether heating the mixture to a temperature above 100° C. and is separated from ethyl acrylate by distillation and re recovering ethyl acrylate. acting said diethyl ether with sulfuric acid and oleum to form ethyl sulfate for recycle in preparing additional References Cited ethyl acrylate, high boiling acrylic acid and beta-ethoxy UNITED STATES PATENTS ethyl propionate reaction by-products are separated from 2,056,771 10/1936 Crawford ------260-486 ethyl acrylate by distillation and recycled to the acry 2,408,940 10/1946 Mahan ------260-486 lamide sulfate and ethyl sulfate reactor, and sulfuric acid 2,816,135 12/1957 Healy ------260-486 is recovered from said reactor, concentrated and recycled for use in preparing additional acrylamide sulfate. O FOREIGN PATENTS 6. A method for preparing ethyl acrylate which com 1,332,186 6/1963 France. prises reacting acrylamide sulfate and ethyl sulfate by mixing ethyl sulfate with acrylamide sulfate in dilute LORRAINE A. WEINBERGER, Primary Examiner. aqueous solution at a temperature below 85° C. and ALBERT P. HALLUIN, Assistant Examiner.